Measuring and testing method and apparatus employing x rays



F. FUA ET AL MEASURING AND TESTING METHOD AND APPARATUS EMPLOYING X-RAYS7 Sheets-Sheei 1 Oct. 10, 1950 Filed Oct. 16, 1944 Oct. 10, 1950 F. FUAETAL 2,525,292

MEASURING AND TESTING METHOD AND I APPARATUS EMPLOYING X-RAYS Filed Oct.16, 1944 7 Sheets-Sheet 2 N P04551437- C7 l Vo'aas BY 7 v y w ATTORN EYOct. 10, 1950 F. FUA ETAL MEASURING AND TESTING METHOD AND APPARATUSEMPLOYING X-RAYS 7 Sheets-Sheet 5 Filed Oct. 16, 1944 A mam Y Nfi (BS TN a 2 8 m & Q 4 $4 7 JWJAV \V vwg M 2 NJ J l f f f m8 /f/ r fl H 7 sv/ QQ m w% QM Ww \\7 N a g n w m m w M Q IL n m mm m m 2 \w TL Oct. 10-,1950 F. FUA ETAL 2,525,292

' MEASURING AND TESTING METHOD AND v APPARATUS EMPLOYING X-RAYS FiledOct. 16, 1944 7 Sheets-Sheet 4 INVENTOR f Pfaf/P C /7//) 4 0547??- 5 1 10005 ATTORN EY F. FUA ET AL MEASURING AND TESTING METHOD AND 7Sheets-Sheet 5 Filed Oct. 16, 1944 RM w o W E T m m b /O NPT T Oct. 10,1950 F. FUA EI'AL 2,525,292

MEASURING AND TESTING METHOD AND v APPARATUS EMPLOYING X-RAYS Filed Oct.16, 1944 7 Sheets-Sheet 6 W E: [j )1} :3 4;

: i ffl/ i :l: w L/ INVENTOR Oct. 10, 1950 F. FUA ETAL 2,5 5,292

MEASURING AND TESTING METHOD AND APPARATUS EMPLOYING X-RAYS Filed Oct.16, 1944 7 Sheets-Sheet 7 Patented Oct. 10, 1950 MEASURING AND TESTINGMETHOD AND APPARATUS EMPLOYING X RAYS Frederic Fua, New York, N. Y., andRobert G. I

Woods, Montclair, N. J., assignors to Standard I Electronic ResearchCorporation, New York, N. Y., a corporation of New York ApplicationOctober 16, 1944. Serial No. 558,928

11 Claims. 1

This invention relates to measuring and testing apparatus, and moreparticularly to methods and apparatus for examination of materials byX-rays or similar penetrating radiations.

A principal object of the invention relates to an X-ray testing devicewhich is capable of ascertaining the internal physical condition ofvarious articles.

Another object relates to an X-ray testing device which is useful in thecontinuous testing or checking of one or more physical characteristicsof a moving object, such for example as an insulated cable as it leavesthe cable insulation sheathing machine.

Another object is to provide an improved X-ray method and apparatus fortesting the thickness or other physical properties of a continuouslymoving fragile web, such as a metal foil, without a physical contacttherewith.

In certain of the arts, for example in the manufacture of insulatedconductors, it is of extreme importance that the cable or metallicconductor be sheathed uniformly with insulation. That is to say, theinsulation thickness should in most cases be uniformly distributedaround the periphery of the conductor. Thus in the case of a singleconductor cable, the conductor should be located concentrically withrespect to the insulation sheath throughout its entire length. Incertain processes of sheathing the wire with insulation, the insulationis extruded or forced through a suitable die or gate through which thecable conductor wire is simultaneously fed. Notwithstanding the mostelaborate precautions to maintain the extruding mechanism clean andaccurate, it very frequently happens that the insulation is not alwaysuniformly distributed around the wire. If the insulation is in plasticcondition during the extrusion, and if the extrusion gate or die becomesclogged at one or more points, there is a tendency for the plasticinsulation to accumulate in a localized region within the die. Thisresults in a non-uniform pressure which tends to offset the wire andinsulation sheath with respect to each other. The net result is that thecable conductor tends to assume a non-concentric relation within theinsulating sheath. This condition is cumulative, so that after a certainextent of run, the cable conductor is too much eccentric with respect tothe insulation sheath to provide satisfactory protection againstbreakdown at one or more sections of the cable. Heretofore, thisabnormal condition could not be ascertained during the insulatingprocess without stopping the machine at frequent intervals to examinesamples of the sheathed conductor. Furthermore, it was not possible tokeep a continuous check on the concentricity or lack of concentricitybetween the conductor and its sheath. Accordingly, it is a principalobject of this invention to provide a device whereby such a continuouscheck can be kept on the relation between a metallic conductor and itsenclosing sheath.

Another feature of the invention relates to a compact X-ray testingdevice which can be installed directly adjacent the exit end of a wireinsulating machine, to determine continuously and instantaneously anyoffsetting of the conductor with respect to the insulation.

Another feature relates to an improved X-ray testing head for examininginsulated electric conductors whereby the insulation can be testedwithout subjecting the cable to deformation or excessive rubbing.

A further feature relates to an X-ray testing head for insulatedelectric conductors whereby the conductor itself acts as part of aspecial X- ray slit system, to determine concentricity or lack ofconcentricity between the conductor and its surrounding insulationsheath.

A further feature relates to a speciall constructed X-ray testing headfor examining insulated cables and the like, which is safe and reliablein operation.

A further feature relates to an X-ray device for testing insulatedconductors to determine the direction and extent of any ofisetting ofthe conductor within its insulating sheath.

Another feature relates to an X-ray device for testing the thickness ofmaterials such as metal foil webs, whereby greater sensitivity intesting thickness or density variations is attained.

Afurther feature relates to an X-ray testing device for testingvariations in thickness or density across the width of a moving metalweb, such for example as a continuously moving metal 3 parts whichcooperate to produce a compact, safe and reliable X-ray testing deviceof the character to be described.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detailed descriptionsand the appended claims.

While the invention will be described in connection with the testing ofinsulated wires, metal foil and the like, it will be understood that incertain of its aspects, the invention is equally well applicable torthetesting of a wide variety of articles. Therefore in the drawing,

Fig. 1 is a side elevation of a cable testing head and X-ray unitaccording to the invention.

Fig. 2 is a sectional planview of Fig. 3, taken along lines 2--2thereof, viewed in the direction of the arrows.

Fig. 3 is a sectional view of Fig. 2, taken along lines 3-3.

Fig. 4i is a left-hand end view of Fig. 2.

Fig. 5 is a partial plan sectional view of Fig. 4, taken along lines 5-5thereof.

Fig. 6 is an end view of a modification of Figs. 1 to 5.

Fig. 7 is a side elevation view of Fig. 6.

Fig. 8 is an end View of a modification for testing the edge of metalwebs,

Fig. 9 is a top-plan view of Fig. 8.

Fig. 10 is an end view of a modification of Figs. 8 and 9.

Fig. 11 is a top-plan view of Fig. 10.

Fig. 12 is a sectional view of Fig. 3 taken alon line l2l2 thereof.

Fig. 13 is a modified form of adjustable slit unit be removablyfastened. Housing [5 is provided on its interior with suitable supportsfor the X-ray tube and its accessories all of which are wellknown in theX-ray art, the electric power supply for the X-ray tube being providedthrough conductors i9, 20. housing 35 is arranged to register with acorresponding window 2 in the plate I. When the two windows are inproper registry, the housing may be fastened in place.

The unit i6 comprises a main body section 22 which may be in the form ofa circular casting having flat end walls 3 to which correspondingrectangular metal blocks 23, 24, are fastened as by screws 58. Fastenedbyscrews 5 to the upper face of member 22 is another casting 3! having acentral circular window 40 which registers with window 2; The casting3.! also has on its lower side a rectangular opening 4|, which isslightly larger than the circular window to form a fiat shoulder 8 whichwith the flat upper face of member 22, provides parallel channels orguides for the adjustable slit unit 32.

As shown in Fig. 5, the slit unit 32 comprises a pair of side bars 35between which are fastened two flat metal blocks 33, 34, by meansofscrews 38. Each of the blocks 33, Sll, is provided with a notched orcut away portion at one end so that when the blocks are fastened inabutting relation as shown in Fig. 5, they define two separate slits 36,3?, which are staggered symmetrically on op-..

The window in the bottom of posite sides of the center line L betweenthe blocks. The notches are of such dimensions that each has a width WWwhich is substantially equal to the radius of the metal conductor orconductor group 41 in the cable 55 to be tested, the insulation coveringor sheath of which is indicated by the numeral 45. The slit unit 32 isslidable for adjusting the slits 36, 3?, laterally with respect to thecenter line L so that the slits can be aligned vertically with thecentral longitudinal axis of the cable ,wire 4?. For this purpose,adjustable stop screws 39 are threaded diametrically opposite to eachother through the wall of member 3i.

Fastened by screws 62 to the flat outer faces of blocks 23 and 24, aretwo circular headers 25,

'25, each having circular bores 55, H, in alignment with correspondingcircular cores in the blocks 23, 24. Likewise, member 22 has a pair oftransverse circular bores 52 and El, which are in alignment with therespective bores in members 23, 24, 25, 25. The upper wall of member 22is provided with a pair of through openings or windows as, with whichthe slits 36, 3? are adapted to register in a vertical direction (Fig.3). Thus when there is no cable passing through the device, there are apair of unobstructed paths for the X- rays through the opening 2, thencethrough slits 36, 3?, thence through openings is into the bore orchamber 5!. However, in order to guide the cable through the device fortesting and to insure that it remains in a fixed longitudinalorientation with respect to the openings 58, there is provided aremovable hollow mandrel which may be made in two sections 27:, 28,although preferably a single length mandrel is employed.- The mandrelextends completely through members 2226. The mandrel is provided withdiametric opposite windows or openings 55, which are arranged toregister with openings 48. When the mandrel openings are in the properregistry, the mandrel can be locked in place by a pair of externallyadjustable set screws 29, 30.

Arranged to pass through the openings 55 in members 23, 25, are a pairof light sensitive or photo-electric cells 52, 53, .of any well-knownconstruction, preferably of the type having a photo electron-emissivecathode and one or more electron collecting electrodes or anodes. Forexample cells which are sold under the trade designation RCA 929, may beused. The cells are mounted so that each has its photo-sensitiveelectrode in alignment with the corresponding slits 55, 52.Consequently, each cell will respond only to the X-ray beam passingthrough the corresponding slit 35 or 5?. The cells may be plugged intorespective contact headers or sockets 55, 56, of any well-knownconstruction, the connecting wires to which are brought out in a commoncable 5! or 58. The sockets 55, 55, may be fastened to 'form a unit withthe respective members it, so

that when the later members are fastened by appropriate screws to clampsto the blocks 22, 23, the cells are correctly connected in circuit andin proper location within chamber 5!.

As shown schematically in Fig. 1, each cell is connected to itsrespective amplifier HA or llB, each of which in turn'controls arespective indicating device or meter 59, 65. The entire testing unitcan be fastened to a suitable common support or table, while theamplifier and indicating equipment may be located at any suitable place.

In using the device to test a cable 45 for offsetting of the wire 41,the slit and amplifier systems are preferably initially adjusted byusing a amazes short length of standard cable which can be insertedthrough the mandrel. Therefore, the central conductor of the standard islocated on the center line of the various windows 48, 49, it beingunderstood that the mandrel has previously been "properly adjusted sothat the windows 48, 49, are in alignment. The slit unit 32 is thenadjusted by. screws 39 until the center line L (Fig. 3) is in verticalalignment with the center of windows 48. This alignment can be effectedeither by .visual examination or by special aligning gauges. The X-rayand amplifier units are then switched into operation and the slit unit32 is again adjusted until both meters 59, 69, read alike. Their settingwill then correspond to perfect concentricity of the cableconductor-within its insulating sheath. It should be observed that theradius of wire 41 of the standard cable is approximately the samedimension as the width of each of the slits 36, 31, so that when theparts are properly adjusted the cable wire acts as a mask, one half ofthe wire thickness masking the cell 52 from the X-rays, and the otherhalf of the 'wire thickness mas-king the cell 53 from the -X-rays. Itwill be understood that the invention is not limited to a completemasking of the respective cells by the corresponding-half of the wire,as it will be clear that a zero or normal reading on the indicators 59,69, can be obtained even if the wire does not entirely mask the slit. Inother words with a standard cable in the device, the zero setting ofindicators 59, 69, may be noted so that when a cable to be tested ispassed through the mandrel, any departure from the standard conditionswithin the cable can be im-- mediately observed.

Because of the symmetrical disposition of the slits 36, 31, on eitherside of the central longitudinal axis of the cable, if the cable undertest has an abnormal condition wherein the wire is offset from thecenter, a particular one of the slits 36, 31, will be completely ormaterially uncovered to cause the corresponding indicator to move to anoff normal position. It will be understood that the device may beprovided with sets of slit units of different slit widths for use intesting cables of different wire size. Likewise, different mandrelshaving the same outside diameter,

but of different inside diameter, may be used for cables of differentoverall diameter.

Instead of using different slit units for testing difierent size wirecables and with the mem- .bers 33, 34, fastened together as a unit, eachof these members 33, 34 may be adjustable towards and away from eachother to vary the widths of :unit may be provided through which thecable (also passes, but with the various slits and the X- ray beamlocated at right angles to the position of the beam and slits asillustrated in the embodiment of Fig. 3.

As a modification, the device already described instead of being mountedon a fixed base or table,

may be mounted for rotation around the cable while the latter is beinfed through the device for testing. Such an arrangement is shown inFigs. 6 and 7. In this embodiment, the X-ray generator unit I9 and theslit-light cell unit H sired angle without disturbing the electricalconare the same as those already described and are fastened together asan assembly. This assembly is suitably supported on a rotatable framewhich is provided with tubular extensions I5, which may be fastened inany suitable manner to the extended ends of the mandrel I6. The ends ofthe mandrel I6 are rotatably supported in journals I4 carried byuprights I3 attached to the table 12. By means of a suitable lever 8|attached to the assembly, the latter may be rotated in unison around thecable I8 to any desired angle. It will be understood of course that theconnecting leads I! for the X-ray unit I0, and the connecting leads .19for the light cell unit II are sufficiently flexible to allow turning ofthe assembly through the denections and without interfering with thefeeding of the cable. By means of a suitable dial, the particularangular setting of the assembly can be determined. Since structurallyand electrically the units I9 and II are the same as those alreadydescribed, the manner of adjusting the slits, and also the indicatorunits which are connected to cables I9 and 80, and their method of useare the same as already described.

Referring to Figs. 8 and 9, there is shown an arrangement for testingthe thickness or density of continuously moving webs such as metal foilwebs. The device comprises a metal housing 9I having a rectangular bore98 extending entirely through its length and through which the metal web94 to be tested is continuously fed. The housing 9i also has a cavityI09 in which is placed a standard sample 95 of the metal foil of knownthickness and density. Communicating with the cavity I00 is a slit IOIthrough which the X-rays from the X-ray tube I92 pass. Likewise a slitI03 communicates with the bore 99 but adjacent one side only of the boreso that the X-rays impinge only on the longitudinal edge of the web 94.Mounted in a suitable cavity beneath the bore 98 and beneath the cavity95 are a pair of photo-electric cells 92, 93. These cells are mounted sothat cell 92 responds only to the X- rays which pass through the edge ofthe web 94;

while the cell 93 responds only to the X-rays which pass through thestandard 95. Each of the cells 92, 93 is connected over conductors 96,9'1 to its respective amplifier as in Fig. 1, to operate a correspondingmeter or indicator. By confining the examination to the longitudinaledge of the web '94, greater sensitivity is obtained in the measurementof the web thickness or density. If the entire width of the web weresubjected to the X-rays there wouldbe an averaging effect over theentire width and local minor changes in thickness or density might givean improper indication of the actual thickness of the web.

Referring to Figs. 10 and 11, there is shown a. device for measuring thedensity or thickness at any particular point or points across the widthof the web while the latter is being fed continuously in the directionof its length. The device comprises abase I I9 having a pair of paralleluprights I I8 between which a pair of guide bars I I! extend; Adapted toslide along the bars I II is a metal housing III) containing on itsinterior an X-ray generator tube I I I, a, light-sensitive orphoto-electric cell H2 and a, receptacle II5 containing a standardsample I I6 of known thickness and density. It will be understood ofcourse that suitable slits I20, I2I are provided between the Xray tubeII I and the photo-electric cell I I2. The housing III] also has asection I22 within which is enclosed another photo-electric cell I23which is provided with a $111; memberIM so that the X-rays from'tub'e III also pass throughsald slit to the cell I23. The sections I22 and I25of the housing Iii! have a ree'ntrant clear portion I26 and the metalfoil or web I21 to be examined is supported on suitable guides (notshown) so as to be fed in a plane perpendicular to the X-ray beam I28.When it is desired to test only the edge section of the web 127, theentire unit II'IB is held in the position shown in Fig. 10.- If,however, it is desired to examine any particular sec tion of the widthof the web I21 while the latter is being fed in the direction of thearrows, the entire unit H0 is moved towards the right, under control ofa suitable lever I29. I

While certain particular embodiments have been disclosed herein, it willbe understood that various changes and modifications may be made thereinwithout departing from the spirit and scope of the invention. It will beunderstood that e the X-rays arechosen as to hardness or penetratingpower so that very little, if any, can escape through the metal walls ofthe various housingsand castings, which are preferably of brass, or someother equivalent metal or alloy.

What is claimed is: V

1. Apparatus for detecting symmetry or. lack of symmetry of location ofthe conductor of a sheathed cable with respect to its enclosing sheathincluding, in combination, a body member provided with a bore throughwhich the sheathed cable can be moved axially, said bore being of adiameter appropriate to hold the sheathed cable coaxial therewith, apair of slits intersecting said bore, said slits being symmetricallydisposed on opposite sides of the axis of said bore, a source of X-rayarranged at one side of said body member and disposed so that said slitsserve as passageways for two separate X-ray beams through said bore, apair of X-ray responsive detectors located on the opposite side of saidbody member from said X-ray source and corresponding to said slits, saiddetectors being arranged to be separately excited in response to theX-ray traversing their respective slits, and means for comparing theresponse of said detectors.

2. Apparatus for detecting symmetry orlack of symmetry of location ofthe conductor of. a sheathed cable with respect to its enclosing sheathincluding, in combination, a body member provided with a bore throughwhich the sheathed cable can be moved axially, said bore being of adiameter appropriate to hold the sheathed cable coaxial therewith, apair of slits intersecting said bore, said slits being symmetricallydisposed on opposite sides of and with one edge coincident with the axisof said bore and staggeredalong said axis, a source of X-ray arranged atone side of said body member and disposed so that said slits serve aspassageways for two separate X-ray beams through said bore, a pair ofX-ray responsive detectors located on the opposite side of said bodymember from said X-ray source and corresponding to said slits, saiddetectors being arranged to be 'separatelyexcited in response to theX-ray traversing their respective slits, and means for comparing theresponse of said detectors.

3. Apparatus for detecting symmetry or lack of symmetry of location ofthe conductor of a sheathed cable with respect to its enclosing sheathincluding, in combination, a body memberprovided with a bore throughwhich the sheathed cable can be moved axially, said bore being of adiameter appropriate to hold the sheathed cable coaxial therewitna pairof slits intersecting said bore, said slits being symmetrically disposedon opposite sides of the axis of said bore, the combined sheath of saidslits transverse to said axis being substantially the width of theconductor of the cable under examination, a source of X-ray arranged atone side of said body member and disposed so that said slits serve aspassageways for two separate X-ray beams through said bore, a pair ofX-ray responsive detectors located on the opposite side of said bodymember from said X-ray source and corresponding to said slits, saiddetectors being arranged to be separately excited in response to theX-ray traversing their respece blVe slits, and means for comparing theresponse of said detectors.

4. Apparatus for detecting symmetry or lack of symmetry of location ofthe conductor'of .a sheathed cable with respect to its enclosing sheathincluding, in combination, a body member provided with a bore, a hollowcable-receiving mandrel passing through said bore through which thesheathed cable can be moved axially, said mandrel being of an insidediameter appropriate to hold the sheathed cable coaxial therewith, aslit unit mounted in said member and intersecting said bore, said unithaving a pair of slits symmetrically disposed on opposite sides of theaxis of said bore, opponents in the wall of said mandrel correspondingwith said slits, a source of X-ray arranged at one side of said bodymember and disposed so that said slits serve as passageways ior twoseparate X-ray beams through said bore, a pair of X-ray responsivedetectors located on the opposite side of said body member .from saidX-ray source and corresponding to said slits, said detectors beingarranged to be separately excited in response to the X-ray traversingtheir respective slits, and means for comparing the response of saiddetectors.

5. Apparatus according to claim 4 in which the slit unit is providedwith means to adjust said unit with respect to the mandrel accurately tolocate its slits symmetrically on opposite sides of the mandrel axis.

6. Apparatus according to claim 5 in which the slit unit comprises apair of abutting metal blocks each having an end notched to provide aslit in cooperation with the abutting unnotched edge of the other block.

7. Apparatus according to claim 6 in which means are provided inadjusting the width of the slits without disturbing a symmetricallocation on the opposite sides of the mandrel axis.

8. Apparatus according to claim 6 in which the source of X-ray and thedetectors are affixed to the body member as a common assembly and meansare provided to rotate said assembly around the cable to .measure theconcentricity of its sheath and conductor in any desired plane Withoutinterfering with the movement of said cable through the mandrel.

9. Apparatus according to claim 8 in which signal indicator meansresponsive to the detectors and to the position of its assembly inrotation of .its cable are provided to indicate the concentricity of theconductor in the sheath and the plane of measurement of theconcentricity so indicated.

10. The method of detecting symmetry or lack of symmetry of location ofone bounded body'o'f material within another bounded bodyof a materialof diiierent radiation absorptivity which comprises passing penetratingradiation through both bodies of material divided into two beams offixed mutual relative incident intensity symmetmaterial to compare theabsorptivity of their re- 5 NI ED TA PATENTS spective pathstherethrough. 5

11. The method of detecting symmetry or lack ggi i N of symmetry oflocation of the conductor of a 2237811 3 1 1941 sheathed cable withrespect to its enclosing 2'264725 Shoup E 1941 sheath which comprisespassing X-ray through 10 2298942 Hicks p 1942 the sheathed cable dividedinto two beams of equal 2301251 Capen 1942 intensity symmetricallydisposed on opposite sides 2433558 1947 of the axis of the sheathedcable and separately 2,525,292 9 rioally disposed on opposite sides ofthe center REFERENCES CITED line of symmetry of the enclosing of Thefollowing references are of record in the terial and separatelymeasuring the radiation in file of this patent: said beams after passingthrough both bodies of measuring the X-ray in said beams after passingthrough the sheathed cable to detect any difler- 15 ence in its residualintensity.

FREDERIC FUA. ROBERT C. WOODS.

